The use of liquid distribution units and liquid distribution assemblies employing such units to distribute liquids over a surface area, for example, the surface of a bed of packing material in a fractionating column, is well-known in the art. As employed in the fractionating column art, these liquid distribution units are composed of various types in which the liquid entering the fractionator is distributed by means of notches, weirs, orifices, sprays, etc. Typical liquid distribution assemblies include those known in the art as a box-type, a sieve-type, a ringset-type, a straight-tube sparger-type or a shower-head type. Further, well-known in the art are spray nozzle distributors, drip-pan distributors, notched-trough distributors and drip-tube pan distributors. The purpose of such distribution assemblies used in the art is to break up the entering liquid, which enters the distributor through one or more liquid inlets, into numerous separate streams for even distribution of the liquid over some surface area. The reason for this is that, for example, in the fractionization art, the extent to which the packing bed is wetted is a major determining factor in the separating efficiency of the fractionating tower. It is well-known in the art that the initial distribution of liquid onto the surface of the packed bed is essential to the ultimate performance of the fractionating unit. The above-noted distribution assemblies used in the art are varied, depending upon the requirements of the vapor-liquid traffic in the column, the cleanliness of the liquid entering the column and the process conditions encountered, for example, temperature, corrosion, pressure, etc.
While the present invention may find utility for liquid distribution in other environments, it is particularly adapted for liquid distribution in packed column fractionation units. An example of a typical packed column fractionation unit known in the art is shown in FIG. 1. Typical fractionating columns are equipped with a packing-type device. Packing devices can be categorized into two types known in the art, random packing and structured packing. Apart from the liquid distribution assembly, the particulars of the fractionating column and specifically the particulars of the packing used, form no part of the present invention.
It is known in the art that the design of liquid distribution assemblies currently used in the art has resulted in unreliable performance due to the fact that such assemblies are subject to inaccurate streams of liquid and to plugging due to contamination and fouling of the various orifices, weirs, spray-nozzles, etc. The result of this is that the fractionating tower performance changes with time or with changes in liquid flow. At present, the art depends on accurate estimates of the rate of liquid flow for the type of distributor used, as well as the size and distribution of the orifices, weirs, tubes, etc. Taking into account known principles of hydraulics, these types of devices can be made to operate properly. However, due to changes in flow, plugging, fouling and various controls implemented during the operation of the fractionation tower, the performance of these devices will change during operation. It can be seen, that while liquid distribution elements and assemblies thereof exist in the art, such liquid distribution elements and assemblies thereof have been less than satisfactory. Recognizing the need for an improved liquid distribution element for incorporation into a liquid distribution assembly, it is a general object of the present invention to provide a liquid distribution element to regulate liquid flow for the purpose of distribution of liquid over a surface area with the capability of varying the flow through individual liquid distribution elements and, further, the capability of cleaning the elements by means operated externally of the fractionation column, without the need for shutting down the operation of the column to allow internal access for the purpose of cleaning or adjusting the liquid distribution elements. In this manner, the improved liquid distribution element and liquid distribution assembly comprising a plurality of such elements enhances the accuracy and operating life of the liquid distribution assembly, and allows for cleaning and adjustment of the individual liquid distribution elements with the fractionation process underway.
A feature of the present invention is to provide a modified pan-type liquid distribution assembly. Such pan-type liquid distribution assemblies are known in the art and employ distribution tubes. These have been designed to give a very efficient form of distribution. However, the art has been somewhat discouraged from the use of this type of distributor, even though it is of relatively simple construction, because of fouling and plugging of the liquid pour points. A feature of the present invention is to provide a means for the regulation of the flow through such distribution tubes and, at the same time, provide for a means for clearing the collection of unwanted fouling material which, in the past, has served to detract from the operation by plugging or partially plugging the liquid pour-points. Another feature of the present invention is to provide a means for performing the adjustment of the flow through, and/or, the unfouling of, the liquid pour-tubes from a point external of the fractionator, so as not to interfere with the ongoing operation of the fractionation column. A further feature of the present invention is the ability to adjust liquid flow through each individual tube to alter the distribution pattern of the liquid across the top of the packed fractionation bed to improve the operation of the fractionation column, again with the adjustment being made with the process underway from external to the fractionation column.
The above features and advantages of the present invention have been described generally in order that the more detailed description which follows may be better understood and in order that the contribution to the art may be better appreciated. These and other features of the present invention will be apparent to those of ordinary skill in the art with reference to the detailed description which follows and the accompanying drawings in which like reference numerals have been used to identify like elements.